1. Technical Field
The present invention relates to a load sensor, a pinch detection apparatus and a load detection apparatus.
2. Prior Art
As a conventional load sensor, there is a load sensor described in the Unexamined Japanese Patent Application Publication No. Hei10-281906. As shown in FIG. 10, this load sensor is formed by forming an air gap 1a extending in a longitudinal direction inside an elongated-shaped elastic insulator 1 and burying plural electrode wires 3A to 3D spaced in a circumferential direction inside a wall thickness of the elastic insulator 1L . The plural electrode wires 3A to 3D are buried so as to twist the wires together spirally around the air gap 1a, and a part of a circumferential segment of the outer circumferential surface is exposed to the air gap 1a. Then, when the elastic insulator 1 is elastically deformed so as to squeeze the air gap 1a by application of a load, it is constructed so that the electrode wires 3A to 3D make contact mutually to conduct and a load is detected.
As a manufacturing method of this load sensor, there is proposed a method for making a twisted wire by twisting a spacer with the same shape as the air gap 1a and the plural electrode wires 3A to 3D together and covering the twisted wire with the elastic insulator 1 and then making the load sensor by pulling the spacer.
Problems to be Solved
However, in the conventional load sensor described above, due to its structure, there is a problem that complicated manufacturing processes of twisting of the spacer and the electrode wires 3A to 3D and subsequent pulling of the spacer are required and the cost is high.
Also, since means for actively separating the electrode wires 3A to 3D mutually to insulate them is not provided, there is also a problem that in the case of bending and placing the load sensor, the electrode wires 3A to 3D accidentally make contact in its bent portion and false detection may occur.
Therefore, in view of the problems, a first object of the invention is to provide a load sensor in which a structure is simple and manufacture can be performed easily at low cost, and a pinch detection apparatus and a load detection apparatus using the load sensor.
Also, a second object of the invention is to provide a load sensor capable of functioning properly even in the case of bending and placing at a large curvature, and a pinch detection apparatus and a load detection apparatus using the load sensor.
Technical means for achieving the object is a load sensor in which first and second electrode members oppositely placed make contact mutually to conduct electrically by application of a load and thereby the load is detected, and the load sensor is characterized by comprising an elastic tube in which at least a part of the circumferential segment is formed into a conductive portion having elasticity, the elastic tube being provided as the first electrode member and formed of elastic material, a center electrode member in which at least the outer circumferential portion has conductivity, the center electrode member being provided as the second electrode member and having a foldable elongated shape elongated in one direction and provided within the elastic tube, and an insulating linear member in which at least the outer circumferential portion is an elongated shape having insulation properties, the insulating linear member being wound spirally on the center electrode member at a predetermined winding distance.
The insulating linear member preferably comprises a first metal wire, and an insulating coat layer applied and formed to a surface of the first metal wire.
Also, the insulating linear member preferably comprises a first metal wire, and a resin coat formed by extrusion molding an insulating resin to a surface of the metal wire.
Further, the insulating linear member is preferably a string-shaped member or a fiber-shaped member formed of insulating material.
Also, the center electrode member preferably comprises a center member having a predetermined tensile strength and restoring properties to folding deformation and having an elongated shape in which at least the outer circumferential portion has elasticity, and a second conductive metal wire transversely wound spirally on the outer circumference of the center member.
Further, the center electrode member preferably further comprises a conductive coat layer made of conductive resin or conductive rubber provided so as to cover the outer circumferential surface of the center member from the upper portion of the second metal wire.
Also, the center electrode member is preferably constructed by twisting or bundling plural metal strands together.
Further, the center electrode member is preferably constructed by a single metal wire.
Also, the load sensor preferably further comprises an outer enclosure tube which is formed of elastic material and encloses the outside of the elastic tube.
Further, technical means for achieving the object is a pinch detection apparatus for detecting a pinch of foreign matter at the time when an opening portion switched by a switching member is closed by the switching member by load detection means provided in at least any one of the opening portion and the switching member, and the pinch detection apparatus is characterized in that the load sensor as defined in any of claims 1-9 is used as the load detection means.
Also, technical means for achieving the object is a load detection apparatus for detecting a load by load detection means placed in a two dimensional manner, and the load detection apparatus is characterized in that the plural load sensors placed in a two dimensional manner as defined in any of claims 1-9 are used as the load detection means.
Further, technical means for achieving the object is a load detection apparatus for detecting a load by load detection means placed in a two dimensional manner, and the load detection apparatus is characterized in that the load sensor bent and placed in a two dimensional manner as defined in any of claims 1-9 is used as the load detection means.